Abstract

An improved bi-material beam theory with adhesive interface is presented to study the interface behavior in a conventional material (e.g., wood or concrete) beam reinforced by an externally bonded (e.g., steel or FRP) plate. Both the adherend normal and tangential deformations induced by interface stresses are considered by introducing two interface compliances, from which an improved solution of interface stress distributions is obtained. In addition, an unrealistic restriction of the same curvatures in both the adherends commonly used in most of the existing studies is released in the present theoretical formulation. Closed-form solutions of interface stresses are derived, and favorable agreements between the present solutions and those of the literature are achieved, thus demonstrating the validity of the solutions. The effects of the adherend normal and tangential deformations on the interface stress distributions are studied, and the improved accuracy of the present flexible interface over the rigid interface is illustrated. The present improved bi-material beam theory provides a better prediction of the interface stress distributions, especially for adherend materials (i.e., beam and bonded plate) made of relatively low stiffness properties (e.g., wood material as the originally strengthened beam and thin FRP composite as the strengthening plate), and it can be used to analyze the interface debonding in the beams with externally adhesive bonded plates.